You should check exposure on camera's LCD after each shot, so you don't end up with 1000 lousy pics from the trip, you may not do again for long time. There is even a graph showing you RGB levels, if you don't trust small LCD display.

I would suggest full reset first, maybe you missed something. If that doesn't help, then I would play with settings: exposure compensation, color saturation, make sure you're set for sRGB, not Adobe RGB etc. How about your monitor, is it at least in the ballpark of being properly calibrated? Without seeing the pictures and reading EXIF it is hard to say what exactly the problem is, but if you need to compensate exposure more than 1/2- 1 F-stop to get it right, maybe there is something wrong with camera or lens, could be iris not closing aperture properly for example. My camera takes great pictures with proper exposure without any tinkering, so there is something wrong with yours albeit just yesterday I took few flash pictures of my daughter and they were all way overexposed, I went to the flash menu, double checked all the settings and I don't even remember changing anything, but all is fine now, so I Just need to watch it, if it happens again.